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00_NOP writes "The political battle over Scotland's independence ballot — to take place in September this year — has now moved on to how the BBC project the UK on their national weather forecast. The BBC use a projection based on the view of Britain from geostationary weather satellites and so there is naturally some foreshortening at the northern end of Britain (Scotland, in other words). But nationalist campaigners say this means Scottish viewers are constantly being shown a distorted image of their country which makes it look smaller and hence (in their view) less able to support independence. In response others have suggested that the nationalists are truly 'flat earthers.'"

"England" (or more correctly the rest of the UK, or "rUK" as it's become known - there's Wales and Northern Ireland as well) don't have a say in the decision. The decision either to become an independent country (or not) will be made by the voters of Scotland, and the voters of Scotland alone.

As someone in the rUK all I can do is sit back and accept whatever they decide. That said, I cannot help feeling that if the decision for independence will somehow be influenced on how Scotland looks in the BBC weather map, somewhere the plot has been lost!

It's not Scotland's fault that there is no devolution settlement for England. Personally, I have always thought it ridiculous that devolution is so asymmetrical, with different devolved powers in each of Scotland, Wales and Northern Ireland, and none whatsoever for England. But that isn't Scotland's fault.

Devolution, perhaps, but the asymmetry could have been corrected by Scotland's MPs. Before devolution, English MPs abstained from voting on things that concern only Scotland, so why do Scottish MPs not abstain from things that only affect England (cf. West Lothian question)?

The problem is that any projection of a map onto a flat surface is distorted. There are no un-distorted maps. A map contains serveral classes of important data on a map, and projections mainly affect distances, areas and angles. It is mathematically impossible to have a plane projection of the Earth's surface which correctly displays distances, but you can have a map that preserves angles and a map that preserves areas. You can't have a preservation of both area and angle in the same map though. But both angle-preserving and area-preserving maps are absolutely bad at displaying distances, so most projections in use today try to compromise between areas and angles and still have not too large distortions of distances.

While that's true for maps of large areas of the Earth, the distortions become near-zero for small swaths like the UK. All you need to do is pick a viewpoint directly overhead and at a sufficient distance, which is what the Scottish Independence group is advocating.

This whole thing probably stems from the geometry of geostationary weather satellites. To always generate the same viewpoint from orbit, the satellites have to be located over the equator at 35,786 km in altitude. That means countries further north in latitude are distorted in the weather photos. From the 1960s to 1990s, this was just the way it was. You couldn't do anything about it. So everyone who lived in extreme northern (or southern) latitudes had to live with distorted satellite weather photos of their country.

Starting around the mid 1990s, computers became fast enough to correct this distortion in photos in a reasonable amount of time. You could now generate undistorted weather maps of reasonably small countries like the UK. But over the previous 3 decades, people had gotten used to the distorted view from geostationary satellites. When you see a flat undistorted map of your country with weather on it, you think "Oh, that's just a graphic someone drew." When you see a distorted map of your country with weather on it, you think "Oh, that's satellite imagery."

People innately trust satellite imagery more. It's a picture, taken from space. No manipulation, no airburshing (photoshopping for those of you too young to know what airbrushing is), right? Of course not; you can manipulate satellite photos as easily as you can manipulate photos from your phone camera. But that's not people's instinctive reaction. It's a satellite picture, so that must be what the weather really looks like from space. I think that's what the BBC was trying to go for with their perspective-foreshortened view of the UK for their weather forecasts. It gives it a greater sense of authenticity.

Eventually, as people lose this pro-satellite viewpoint bias, the overhead viewpoint maps are going to become the norm. But for the time being, it's a quick and silent way to tell the viewer "this is satellite imagery" vs "this is radar or an animated graphic."